WILLA TURNS A SLOW CIRCLE on the wet deck, her arms outstretched and her face tilted toward the swirling mist. The force of Niagara Falls crashes over the Hurricane Deck railing, splashing hard against her back and crashing over her head. She shrieks and links forearms with Taylor to keep them both steady, and when they look at each other, they crack up laughing. Water streams into the neckline of Willa’s thin yellow poncho, soaking her T-shirt and her bikini underneath. Her makeup has washed away, but she doesn’t care.

“This is the coolest thing I’ve ever done!” she shouts over the roar as the falls batter the rocks beside the deck. Another wave smashes into her and she shrieks again.

Taylor rolls her eyes, but she’s smiling as she yells back. “You need to get a life.”

“Don’t pretend like you’re not having fun!”

This morning, they boarded a bus in St. Catharines that took them to downtown Niagara Falls, where they rode another bus to the Rainbow Bridge. They crossed on foot, stopping to take pictures of each other with one foot in Canada and the other in the United States, kind of like they’d done on the boat.

The US border guard seems unimpressed that they’d come through the Welland Canal by sailboat. Maybe to him it meant nothing. Maybe to him, Willa and Taylor were just two ordinary tourists. But the guard didn’t know they were doing something important, that they are on a quest.

At the lower levels of the Cave of the Winds tour, the Bridal Veil Falls tumbles over moss-covered rocks, and the photos Taylor took were scenic and beautiful. Now she attempts a selfie with her phone in its waterproof case as they stand with the falls, thundering and white, splashing them from behind. Willa bares fierce teeth, but laughs at the last minute, so she doesn’t know how her face will turn out.

They return to a lower, less-intense deck to have a look at the results. The image is hazy around the edges from the mist and speckled with water droplets. Their hair is dripping, their ponchos are molded to their bodies, and Willa is actually doing the fierce thing with her teeth. But what stands out most is that behind them, shimmering softly in the spray, is a rainbow.

Taylor’s eyes squeeze closed and she draws in a shuddering breath. She is so wet that no one would be able to distinguish tears from water, except Willa. There on the deck, surrounded by the constant rush of the falls and people yelling above it, she slips an arm around Taylor’s shoulder. “It’s okay.”

“I miss her so much,” Taylor sobs. “She should be here.”

Willa has no faith left in the God who took away her best friend, but she touches her finger to the rainbow on the screen. “She’s right here, Taylor. See?”